New research from last week 15/2012

Posted by Ari Jokimäki on April 16, 2012

This week’s shocker is the climate change 4000 years ago that wiped out most of Chinese Neolithic cultures. However, several thousands of years earlier Chinese had it better; climate change back then (known as Younger Dryas event) was much milder in China than in Greenland. I wonder if Greenland was actually green during the YD event, or was it even a “land”. They might have called it Whiteice back then.

By the way, we do have a study on Greenland this week. This one studies supraglacial lakes in West Greenland. You might think that melting is a good thing for lakes as it increases their water amount, but strangely enough, in this case the meltwater apparently drains the lakes. Another study this week studies glacial lakes in Himalaya. There the lakes are quite nasty, as they produce outburst floods. There’s also another study that has mapped all the glacial lakes there. As you can see, in the world of scientists, lakes aren’t just those watery things that lie there without actually doing anything. No, in their world lakes are things that go out in a burst. And some say that science isn’t interesting…

Each week, we usually have many studies concerning biosphere, but this week we only have one study. Gladly that one is a stellar study – it is about a sea star. Well ok, we do have a study on land carbon cycle which largely is about biosphere. We also have a tree ring study which can be considered as biosphere related study. So, perhaps we should just conclude that we have lot of biosphere studies this week. How many Arctic studies we have? There was the Greenland paper (I wonder if in the future paper will actually be important export of Greenland), and then we have the upwelling paper, positive cloud feedback paper, and perhaps even the NAO paper. That would make four papers. We only have one paper from Antarctica – the one on temperature trends. This uneven spatial distibution of papers might be due to my northern bias. After all, part of my home country is in Arctic region.

Two other not yet mentioned studies in this week have been studying urban issues. You will find out how modification of urban surface albedos affects global climate and how methane isotopes in Los Angeles reveal fossil fuel leaks. Hmm… Los Angeles isotopes. That doesn’t sound right. Shouldn’t they have made their study in Springfield?

YD event was more gradual and had smaller amplitude in northern China than in Greenland

Abstract: “A high-resolution and absolute-dated stalagmite record from Kulishu Cave, Beijing characterizes Asian Monsoon (AM) history in northern China between ca 14 and 10.5 ka BP (thousand yrs before present, present = 1950), including the entire Younger Dryas (YD) event. Using 230Th dates and counting of annual-layers, the shift into the YD began at 12,850 ± 40 yr BP and took ∼340 yrs and the shift out of the YD began at 11,560 ± 40 yr BP and took <38 yrs (best estimate ∼20 yrs), broadly similar to previously reported AM records from central and southeastern China. The more gradual nature of the start of the YD event as observed in the AM records appears to contrast with the more abrupt beginning observed in the Greenland ice records. The total amplitude of the AM YD event is also smaller than the amplitude of the AM Heinrich Stadial 1 event. In addition, the general rising trend of the AM during the Bølling-Allerød period contrasts with the general cooling trend in Greenland temperature during that time. The influence of rising insolation on the AM may explain this observation."

Abstract: “The study of pointer years of numerous tree-ring chronologies of the central Iberian Peninsula (Sierra de Guadarrama) could provide complementary information about climate variability over the last 405 yr. In total, 64 pointer years have been identified: 30 negative (representing minimum growths) and 34 positive (representing maximum growths), the most significant of these being 1601, 1963 and 1996 for the negative ones, and 1734 and 1737 for the positive ones. Given that summer precipitation was found to be the most limiting factor for the growth of Pinus in the Sierra de Guadarrama in the second half of the 20th century, it is also an explanatory factor in almost 50% of the extreme growths. Furthermore, these pointer years and intervals are not evenly distributed throughout time. Both in the first half of the 17th and in the second half of 20th, they were more frequent and more extreme and these periods are the most notable for the frequency of negative pointer years in Central Spain. The interval 1600–1602 is of special significance, being one of the most unfavourable for tree growth in the centre of Spain, with 1601 representing the minimum index in the regional chronology. We infer that this special minimum annual increase was the effect of the eruption of Huaynaputina, which occurred in Peru at the beginning of 1600 AD. This is the first time that the effects of this eruption in the tree-ring records of Southern Europe have been demonstrated.”

Most of Chinese Neolithic cultures were destroyed in a climate event 4000 years ago

Abstract: “Our review of recently published climatic proxy sequences shows that the most dramatic climate tranistion of the mid Holocene (~8500–~3500 cal. yr BP) occurred at the middle- to late-Holocene transition at ~4000 cal. yr BP. In northern China, an abrupt climatic shift at ~4000 cal. yr BP was recorded in the eastern margin of the Tibetan Plateau, in the western part of the Chinese Loess Plateau and in the vast Inner Mongolian Plateau. In southern China, the ~4000 cal. yr BP event was also abrupt, but it is expressed as one of several quasi-cyclic events in most of the records. We propose that the cumulative effects of insolation-dictated declining trend in tropical SST and the geologically documented increasing trend of ENSO activity were the first-order causes of the cooling and the associated drying during the past 6000 years. Superimposed on the first-order causes were the second-order causes, i.e. the additive effects of the ‘Bond Event 3’-associated lower insolation and the increasingly drying-resulted negative feedback of ‘air–land interactions’. The second-order causes made ~4000 cal. yr BP the tipping point when the resultant drying had destroyed many Chinese Neolithic cultures. Our review of published archaeological literature shows that six of the seven well-documented Chinese Neolithic cultures collapsed at ~4000 cal. yr BP with the exception of the Henan Longshan Culture that evolved to the more advanced Erlitou Culture. The indicators of the cultural collapse include (1) the number of archaeological sites was significantly reduced, (2) the quality of the archaeological artifacts of the succeeding culture is lower than that of the preceding culture, (3) more sophisticated architectures disappeared, and (4) agricultural cultures were replaced by pastoralism or by agro-pastoralism in northern China.”

Abstract: “The sudden drainage of supraglacial lakes has been previously observed to initiate surface-to-bed hydrologic connections, which are capable of enhancing basal sliding, in regions of the Greenland Ice Sheet where ice thickness approaches 1 km. In this study, we develop a robust algorithm, which automatically detects and tracks individual supraglacial lakes using visible satellite imagery, to document the evolution of a population of West Greenland supraglacial lakes over ten consecutive melt seasons. Validation tests indicate that the algorithm is highly accurate: 99.0% of supraglacial lakes can be detected and tracked and 96.3% of reported lakes are true supraglacial lakes with accurate lake properties, such as lake area, and timing of formation and drainage. Investigation of the interannual evolution of supraglacial lakes in the context of annual melt intensity reveals that during more intense melt years, supraglacial lakes drain more frequently and earlier in the melt season. Additionally, the lake population extends to higher elevations during more intense melt years, exposing an increased inland area of the ice sheet to sudden lake drainage events. These observations suggest that increased surface meltwater production due to climate change will enhance the spatial extent and temporal frequency of lake drainage events. It is unclear whether this will ultimately increase or decrease the basal sliding sensitivity of interior regions of the Greenland Ice Sheet.”

Isotopic measurements show that major source of atmospheric methane in Los Angeles is leakage of fossil fuels

Abstract: “Recent studies have suggested that CH4 emissions in Los Angeles and other large cities may be underestimated. We utilized stable isotopes (13C and D) and radiocarbon (14C) to investigate sources of CH4 in Los Angeles, California. First, we made measurements of δ13C and δD of various CH4 sources in urban areas. Fossil fuel CH4 sources (oil refineries, power plants, traffic, and oil drilling fields) had δ13C values between −45 and −30‰ and dD values between −275 and −100‰, whereas biological CH4 (cows, biofuels, landfills, sewage treatment plants, and cattle feedlots) had δ13C values between −65 and −45‰ and δD values between −350 and −275‰. We made high-altitude observations of CH4 concentration using continuous tunable laser spectroscopy measurements combined with isotope analyses (13C, 14C, and D) of discrete samples to constrain urban CH4 sources. Our data indicate that the dominant source of CH4 in Los Angeles has a δ13C value of approximately −41.5‰ and a δD value between −229 and −208‰. Δ14C of CH4 in urban air samples ranged from +262 to +344‰ (127.1 to 134.9 pMC), depleted with respect to average global background CH4. We conclude that the major source of CH4 in Los Angeles is leakage of fossil fuels, such as from geologic formations, natural gas pipelines, oil refining, and/or power plants. More research is needed to constrain fluxes of CH4 from natural gas distribution and refining, as this flux may increase with greater reliance on natural gas and biogas for energy needs.”

Abstract: “Solar reflective urban surfaces (white rooftops and light-colored pavements) can increase the albedo of an urban area by about 0.1. Increasing the albedo of urban and human settlement areas can in turn decrease atmospheric temperature and could potentially offset some of the anticipated temperature increase caused by global warming. We have simulated the long-term (decadal to centennial) effect of increasing urban surface albedos using a spatially explicit global climate model of intermediate complexity. We first carried out two sets of simulations in which we increased the albedo of all land areas between ±20° and ±45° latitude respectively. The results of these simulations indicate a long-term global cooling effect of 3 × 10−15 K for each 1 m2 of a surface with an albedo increase of 0.01. This temperature reduction corresponds to an equivalent CO2 emission reduction of about 7 kg, based on recent estimates of the amount of global warming per unit CO2 emission. In a series of additional simulations, we increased the albedo of urban locations only, on the basis of two independent estimates of the spatial extent of urban areas. In these simulations, global cooling ranged from 0.01 to 0.07 K, which corresponds to a CO2 equivalent emission reduction of 25–150 billion tonnes of CO2.”

Magnitude of extremely cold temperatures has reduced in Antarctic Peninsula

Abstract: “This study examines the daily observed temperature at the Faraday/Vernadsky station in the Antarctic Peninsula for the period February 1947 through January 2011. Faraday/Vernadsky is experiencing a significant warming trend of about 0.6 °C/decade over the last few decades. Concurrently, the magnitude of extremely cold temperatures has reduced while there is no evidence for an increase of the annual maximum temperature. An empirical mode decomposition reveals that most of the temperature variability occurs on intraannual time scales and that changes in the magnitude of the annual cycle can be explained by a simple periodic stochastic process. Extremely cold temperatures below a threshold follow a generalised Pareto distribution (GPD) with a negative shape parameter and thus are bounded. We find that the extremely cold behaviour in the first half of the record is significantly different from the second half. At the same time there is no evident increase of warm temperatures or in the location of the maximum of the temperature probability distribution. These findings provide evidence that at Faraday/Vernadsky, it is the change in the shape of the temperature distribution that has substantially contributed to the observed warming over the last few decades. Furthermore, we find evidence for clustering of extreme cold events and show that they are predictable a few days in advance using a precursor-based prediction scheme.”

Temperature sensitivity of photosynthetic metabolism is most important uncertainty in land carbon cycle

Abstract: “Unknowns in future global warming are usually assumed to arise from uncertainties either in the amount of anthropogenic greenhouse gas emissions or in the sensitivity of the climate to changes in greenhouse gas concentrations. Characterizing the additional uncertainty in relating CO2 emissions to atmospheric concentrations has relied on either a small number of complex models with diversity in process representations, or simple models. To date, these models indicate that the relevant carbon cycle uncertainties are smaller than the uncertainties in physical climate feedbacks and emissions. Here, for a single emissions scenario, we use a full coupled climate–carbon cycle model and a systematic method to explore uncertainties in the land carbon cycle feedback. We find a plausible range of climate–carbon cycle feedbacks significantly larger than previously estimated. Indeed the range of CO2 concentrations arising from our single emissions scenario is greater than that previously estimated across the full range of IPCC SRES emissions scenarios with carbon cycle uncertainties ignored. The sensitivity of photosynthetic metabolism to temperature emerges as the most important uncertainty. This highlights an aspect of current land carbon modelling where there are open questions about the potential role of plant acclimation to increasing temperatures. There is an urgent need for better understanding of plant photosynthetic responses to high temperature, as these responses are shown here to be key contributors to the magnitude of future change.”

Abstract: “Retreat of Arctic sea ice extent has led to more evaporation over open water in summer and subsequent cloud changes in autumn. Studying recent satellite cloud data over the Arctic Ocean, we find that low (0.5–2 km) cloud cover in October has been increasing significantly during 2000–2010 over the Beaufort and East Siberian Sea (BESS). This change is consistent with the expected boundary layer cloud response to the increasing Arctic evaporation accumulated during summer. Because low clouds have a net warming effect at the surface, October cloud increases may be responsible for the enhanced autumnal warming in surface air temperature, which effectively prolong the melt season and lead to a positive feedback to Arctic sea ice loss. Thus, the new satellite observations provide a critical support for the hypothesized positive feedback involving interactions between boundary layer cloud, water vapor, temperature, and sea ice in the Arctic Ocean.”

Possible link between sunspots and North Atlantic Oscillation

Abstract: “We analyze the periods 1878–1944 and 1944–2008. The quasi-stationary wave in the North Atlantic region was stronger and the baroclinity steeper in 1878–1944 than in 1944–2008. The North Atlantic Oscillation Index—as defined by the Climate Research Unit, University of East Anglia—was higher in the former period too. We illustrate these statements by maps of sea level pressure and air temperature at the surface. The long-term trends in the North Atlantic Oscillation Index are linked to the trend in sunspot number such that when, in the mean, the sunspot numbers were high (Gleissberg maxima) the trends in the two quantities were parallel; and when the mean sunspot numbers were low (Gleissberg minima) the trends in the North Atlantic Oscillation Index and sunspots were opposite. We find the connections between the trends statistically significant, and we infer that the level of solar activity played a role in the trends of the past two centuries in the North Atlantic region. However, we cannot as yet provide a mechanism linking the solar trends to those in the atmosphere and ocean, but as a step toward an explanation, the equator to pole temperature gradient is steeper in a Gleissberg minimum than in a maximum.”

Abstract: “The carbon system of the western Arctic Ocean is undergoing a rapid transition as sea ice extent and thickness decline. These processes are dynamically forcing the region, with unknown consequences for CO2 fluxes and carbonate mineral saturation states, particularly in the coastal regions where sensitive ecosystems are already under threat from multiple stressors. In October 2011, persistent wind-driven upwelling occurred in open water along the continental shelf of the Beaufort Sea in the western Arctic Ocean. During this time, cold (<−1.2°C), salty (>32.4) halocline water—supersaturated with respect to atmospheric CO2 (pCO2 > 550 μatm) and undersaturated in aragonite (Ωaragonite < 1.0) was transported onto the Beaufort shelf. A single 10-day event led to the outgassing of 0.18–0.54 Tg-C and caused aragonite undersaturations throughout the water column over the shelf. If we assume a conservative estimate of four such upwelling events each year, then the annual flux to the atmosphere would be 0.72–2.16 Tg-C, which is approximately the total annual sink of CO2 in the Beaufort Sea from primary production. Although a natural process, these upwelling events have likely been exacerbated in recent years by declining sea ice cover and changing atmospheric conditions in the region, and could have significant impacts on regional carbon budgets. As sea ice retreat continues and storms increase in frequency and intensity, further outgassing events and the expansion of waters that are undersaturated in carbonate minerals over the shelf are probable.”

Abstract: “In areas of high relief, many glaciers have extensive covers of supraglacial debris in their ablation zones, which alters both rates and spatial patterns of melting, with important consequences for glacier response to climate change. Wastage of debris-covered glaciers can be associated with the formation of large moraine-dammed lakes, posing risk of glacier lake outburst floods (GLOFs). In this paper, use observations of glaciers in the Mount Everest region to present an integrated view of debris-covered glacier response to climate change, which helps provide a long-term perspective on evolving GLOF risks. In recent decades, debris-covered glaciers in the Everest region have been losing mass at a mean rate of ~ 0.32 m yr-1, although in most cases there has been little or no change in terminus position. Mass loss occurs by 4 main processes: (1) melting of clean ice close to glacier ELAs; (2) melting beneath surface debris; (3) melting of ice cliffs and calving around the margins of supraglacial ponds; and (4) calving into deep proglacial lakes. Modelling of processes (1) and (2) shows that Everest-region glaciers typically have an inverted ablation gradient in their lower reaches, due to the effects of a down-glacier increase in debris thickness. Mass loss is therefore focused in the mid parts of glacier ablation zones, causing localized surface lowering and a reduction in downglacier surface gradient, which in turn reduce driving stress and glacier velocity, so the lower ablation zones of many glaciers are now stagnant. Model results also indicate that increased summer temperatures have raised the altitude of the rain-snow transition during the summer monsoon period, reducing snow accumulation and ice flux to lower elevations. As downwasting proceeds, formerly efficient supraglacial and englacial drainage networks are broken up, and supraglacial lakes form in hollows on the glacier surface. Ablation rates around supraglacial lakes are typically one or two orders of magnitude greater than sub-debris melt rates, so extensive lake formation accelerates overall rates of ice loss. Most supraglacial lakes are ‘perched’ above hydrological base level, and are susceptible to drainage if they become connected to the englacial drainage system. Speleological surveys of conduits show that large englacial voids can be created by drainage of warm lake waters along pre-existing weaknesses in the ice. Roof collapses can open these voids up to the surface, and commonly provide the nuclei of new lakes. Thus, by influencing both lake drainage and formation, englacial conduits exert a strong control on surface ablation rates. An important threshold is crossed when downwasting glacier surfaces intersect the hydrological base level of the glacier. Base-level lakes formed behind intact moraine dams can grow monotonically, and in some cases can pose serious GLOF hazards. Glacier termini can evolve in different ways in response to the same climatic forcing, so that potentially hazardous lakes will form in some situations but not others. Additionally, the probability of a flood not simply a function of lake volume, but depend on the geometry and structure of the dam, and possible trigger mechanisms such as ice- or rockfalls into the lake. Satellite-based measurements of glacier surface gradient and ice velocities allow probable future locations of base-level lakes to be identified. A base-level lake has begun to grow rapidly on Ngozumpa Glacier west of Mount Everest, and could attain a volume of ~ 108 m3 within the next 2 or 3 decades. Unless mitigation efforts are undertaken, this lake could pose considerable GLOF hazard potential.”

For a sea star species future warming is worse than acidification

Abstract: “Climate change driven ocean warming and acidification is potentially detrimental to the sensitive planktonic life stages of benthic marine invertebrates. Research has focused on the effects of acidification on calcifying larvae with a paucity of data on species with alternate developmental strategies and on the interactive effects of warming and acidification. To determine the impact of climate change on a conspicuous component of the intertidal fauna of southeast Australia, the development of the non-calcifying lecithotrophic larvae of the sea star Meridiastra calcar was investigated in the setting of predicted ocean warming (+2-4°C) and acidification (-0.4-0.6 pH units) for 2100 and beyond in all combinations of stressors. Temperature and pH were monitored in the habitat of M. calcar to place experiments in context with current environmental conditions. There was no effect of temperature or pH on cleavage stage embryos but later development (gastrula-larvae) was negatively effected by a +2°-4°C warming and there was a negative effect of -0.6 pH units on embryos reaching the hatched gastrula stage. Mortality and abnormal development in larvae increased significantly even with +2°C warming and larval growth was impaired at +4°C. For the range of temperature and pH conditions tested, there were no interactive effects of stressors across all stages monitored. For M. calcar, warming not acidification was the dominant stressor. A regression model incorporating data from this study and projected increasing SST for the region suggests an increase in larval mortality to 70% for M. calcar by 2100 in the absence of acclimation and adaptation. The broad distribution of this species in eastern Australia encompassing subtropical to cold temperate thermal regimes provides the possibility that local M. calcar populations may be sustained in a warming world through poleward migration of thermotolerant propagules, facilitated by the strong southward flow of the East Australian Current.”

CLASSIC OF THE WEEK: Stupart (1917)

Abstract: No abstract. A quote from the paper: “The purpose of this paper is to show what indications there may be, if any, that the climate of Canada is gradually changing; whether there is a tendency towards greater warmth or greater cold, or whether the rainfall is increasing or decreasing. Before proceeding, however, I would draw your attention to certain conclusions by recent writers regarding the climate of the past 3,000 years.”

One Response to “New research from last week 15/2012”

barrysaid

Found this interesting paper on Earth’s atmosphere through the ages. No idea where it might belong here, but anyway…

Milestones in the evolution of the atmosphere with reference to climate change

Glikson (2008)

The history of life on Earth is critically dependent on the carbon, sulfur and oxygen cycles of the lithosphere – hydrosphere – atmosphere – biosphere system. An Archean oxygen-poor greenhouse atmosphere developed through: (i) accumulation of CO2 and CH4 from episodic injections of CO2 from volcanic activity, volatilised crust impacted by asteroids and comets, metamorphic devolatilisation processes and release of methane from sediments; and (ii) little CO2 weathering-capture due to both high temperatures of the hydrosphere (low CO2 solubility) and a low ratio of exposed continents to oceans. In the wake of the Sturtian glaciation, enrichment in oxygen and appearance of multicellular eukaryotes heralded the onset of the Phanerozoic where greenhouse conditions were interrupted by periods of strong CO2-sequestration through intensified capture of CO2 by marine plants, onset of land plants and burial of carbonaceous shale and coal (Late Ordovician; Carboniferous – Permian; Late Jurassic; Late Tertiary – Quaternary). The progression from Late Mesozoic and Early Tertiary greenhouse conditions to Late Tertiary – Quaternary ice ages was related to the sequestration of CO2 by rapid weathering of the emerging Alpine and Himalayan mountain chains. A number of peak warming and sea-level-rise events include the Late Oligocene, mid-Miocene, mid-Pliocene and Pleistocene glacial terminations. The Late Tertiary – Quaternary ice ages were dominated by cyclic orbital-forcing-triggered terminations which involved CO2-feedback effects from warming seas and the biosphere and albedo flips due to ice-sheet melting. Since ca AD 1750 human emissions were 305 Gt of carbon, as compared with 750 Gt C in the atmosphere. The emissions constitute 12% of the terrestrial biosphere and 10% of the known global fossil fuel reserve of 4000 Gt C, whose combustion would compare to the 4600 Gt C released to the atmosphere during the K – T impact event 65 million years ago, with associated 65% mass extinction of species. The current growth rate of atmospheric greenhouse gases and global mean temperatures exceed those of Pleistocene glacial terminations by one to two orders of magnitude. The relationship between temperatures and sea-levels for the last few million years project future sea-level rises toward time-averaged values of at least 5 m per 1°C. The instability of ice sheets suggested by the Dansgaard – Oeschinger glacial cycles during 50 – 20 ka, observed ice melt lag effects of glacial terminations, spring ice collapse dynamics and the doubling per-decade of Greenland and west Antarctic ice melt suggest that the Intergovernmental Panel on Climate Change’s projected sea-level rises (<59 cm) for the 21st century may be exceeded. The biological and philosophical rationale underlying climate change and mass extinction perpetrated by an intelligent carbon-emitting mammal species may never be known.